Pneumothorax and pneumoperitoneum were roentgenographically demonstrated and appeared to occur simultaneously in a premature newborn infant with hyaline membrane disease. It was surmised clinically and rotengenographically that the intraperitoneal air had reached the peritoneal cavity from mediastinal or pleural gas, and did not represent a perforated viscus, a finding confirmed by contrast studies and at autopsy. Postmortem examination following death from hyaline membrane disease and intracranial hemorrhage confirmed that there was neither perforation of an abdominal viscus, nor any evidence of peritonitis. This case emphasizes the importance of recognizing that the sudden appearance of pneumoperitoneum in the newborn period may be a complication of pneumomediastinum or pneumothorax or both and that, with appropriate studies, unnecessary laparotomy may be avoided.